The invention relates to a method of operating a headlight having a laser light source in a motor vehicle as well as to a corresponding headlight.
When laser light sources are used in motor vehicle headlights, there is the problem that, as a result of the high luminance of such light sources, eye injuries may occur in other traffic participants in the event of a prolonged blinding caused by the headlight. Such endangering of other traffic participants should be eliminated to the largest extent.
It is therefore an object of the invention to provide a method of operating a headlight having a laser light source in a motor vehicle, so that danger to other traffic participants caused by the laser light source are considerably reduced or eliminated.
This and other objects are achieved by the method according to the invention for operating a laser headlight, and a corresponding laser headlight, which generates a light distribution from the light of a laser light source, which as a rule includes one or more laser diodes. This light distribution may, for example, be a high-beam light distribution or a low-beam light distribution in the far field of the vehicle. The headlight preferably is a front headlight. Within the scope of the method according to the invention, the laser light source of the headlight is activated such that the operating power of the laser light source is switched from a first power value to a deactivated operating state or is reduced to a second (lower) power value, when the speed of the motor vehicle falls below a first speed threshold. Switching to a deactivated operating state is the switching-off of the operation of the laser light source (i.e. operating power of zero). The first power value and the second power value represent operating powers of greater than zero. The first power value may be understood to be a power value that presents the normal operation of the laser light source. The first power value may, for example, represent the maximal operating power of the laser light source.
For activating the laser light source, the method according to the invention also uses a second speed threshold, which is greater than or equal to the first speed threshold. In this case, the operating power of the laser light source is increased from the deactivated operating state or from the second power value to the first power value when the speed of the motor vehicle exceeds the second speed threshold.
The method according to the invention is based on the recognition that, at low vehicle speeds, a traffic participant's eyes may be at a close distance from the headlight and a prolonged exposure of the eyes to the laser radiation of the headlight may occur. At an excessive luminous intensity of the laser light source, this may result in injury to the eye. At low speeds, the laser light source is therefore switched off or, as a result of the lowering of its operating power, the light intensity of brightness is appropriately dimmed. In this case, the operating power is the optical power of the laser light source, which is correlated with the supplied electric power as well as the brightness of the laser light source. A higher optical operating power results in a greater brightness or luminous intensity of the laser light source.
In a preferred variant, the activation of the laser light source is further developed such that, when generating the light distribution by the headlight, the laser light source complies with Class 1 or 1M or 2 or 2M according to the IEC 60825-1 Standard. This standard classifies lasers with respect to the endangerment of the user. The higher the classification number, the greater the danger to the user. The above-mentioned classes are associated with a slight endangerment of the eye. The adaptation of the laser light source corresponding to the above-mentioned standard takes place by establishing the above-defined speed thresholds or power values. Based on the standard, a person skilled in the art can appropriately determine the thresholds or power values for complying with the corresponding class. As required, the activation of the laser light source may also be such that, when generating the light distribution by the headlight, the laser light source belongs to a defined (low) risk group according to the IEC 62471 Standard.
In a particularly preferred embodiment, the first speed threshold is between 20 km/h and 120 km/h, preferably between 20 km/h and 60 km/h, whereas the second speed threshold is between 30 km/h and 130 km/h, preferably between 30 km/h and 70 km/h. Above these thresholds, the danger to the eyes of any traffic participants is negligible because of the high speed of the vehicle. In a further variant, the second power value amounts to 50% or less of the first power value, particularly 25% or less or preferably 20% or less of the first power value. This ensures a strong dimming of the laser light source during a slow drive.
In a further development, the method according to the invention is used for operating a headlight which, in addition to the laser light source, includes at least one additional light source which is constantly switched on for generating the light distribution by the headlight. It is thereby ensured that, also at lower speeds, the generating of the desired light distribution is ensured (with reduced intensity). The at least one additional light source preferably comprises an LED light source, a halogen light source and/or a xenon light source. The glare of these light sources does not endanger the eyes.
As required, the at least one additional light source may also include a further laser light source which, when the light distribution is generated by the headlight, complies with Class 1 or 1M or 2 or 2M according to the IEC 60825-1 Standard. This further laser light source has a significantly lower intensity than the laser light source controlled in the process according to the invention. In particular, independently of the vehicle speed (i.e. also when the vehicle is stopped), it never endangers the eyes of other traffic participants.
In a further embodiment, several different light distributions can be generated by means of the headlight, in which case, the method according to the invention or preferred variants of the method according to the invention are implemented for at least one of the light distributions and, particularly, for each of the light distributions. The different light distributions particularly include one or more (different) low-beam light distributions and/or one or more (different) high-beam light distributions. The method of the invention is preferably implemented for the high-beam light distribution.
In a concrete implementation of the method according to the invention, the speed of the vehicle, which is processed when activating the laser light source, is determined by way of sensor data by one or more rotational wheel speed sensors, the sensor data preferably being stored via a bus (i.e. a data bus) of the motor vehicle and are retrieved via the bus for determining the speed of the motor vehicle.
In a variant of the above-described embodiment, the speed is determined in a central control unit of the motor vehicle, the activating of the laser light source being caused such that the central control unit generates commands for changing the operating power of the laser light source based on the determined speed of the motor vehicle, and based on the commands, a headlight control unit changes the operating power of the laser light source.
These commands permit the activation of the laser light source according to the invention as a function of the first and second speed thresholds as well as based on the first and second power value. In a preferred variant, the commands are placed by the central control unit on the above-described bus and are retrieved from the latter by way of the headlight control unit. Preferably, the central control unit retrieves the sensor data of the rotational wheel speed sensors also from the bus in order to determine the vehicle speed in this manner.
As required, the activation of the laser light source may also be carried out without a central control unit.
In this case, the speed of the motor vehicle is determined in a headlight control unit, the activation of the laser light source being caused by the headlight control unit. In a preferred variant, the headlight control unit retrieves the sensor data of the rotational wheel speed sensor or sensors by way of the above-described bus.
The invention further relates to a motor vehicle, comprising a laser light source from whose light a light distribution is generated during the operation of the headlight. During the operation of the headlight, the laser light source is activated such that the operating power of the laser light source is switched from a first power value to a deactivated operating state or is lowered to a second power value when the speed of the motor vehicle falls below a first speed threshold, and the operating power of the laser light source is increased from the deactivated operating state or from the second power value to the first power value when the speed of the motor vehicle exceeds a second speed threshold which is greater than or equal to the first speed threshold. The headlight according to the invention is preferably set up for the implementation of one or more of preferred variants of the method according to the invention.
Furthermore, the invention relates to a motor vehicle which comprises one or more headlights according to the invention or one or more preferred variants of the headlight according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.
An embodiment of the invention will be described in detail by reference to FIG. 1. This FIGURE is a schematic block diagram view of the components in a motor vehicle by which a variant of the method according to the invention is implemented.